team: handle sending port list in the same way option list is sent

Essentially do the same thing with port list as with option list.
Multipart netlink message.
Side effect is that port event message can send port which is not longer
in team->port_list.

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>